1. Field of the Invention
The present invention relates to a magnetic tape drive, and in particular, to the magnetic tape drive that can form data tracks in a lateral direction in a higher density, compared to a conventional magnetic tape drive.
2. Description of the Related Art
These years in a magnetic tape used for a data backup of a computer and the like, an augmentation of a memory capacity progresses and some magnetic tapes have a capacity of not less than 100 GB (gigabyte). When in such the magnetic tapes data tracks are formed along longitudinal directions (travel directions) thereof, a width of each data track itself and a distance between each data track are narrowed and a number of data tracks are increased, thereby a high density of the data tracks being intended.
In order to record/reproduce data signals on such the magnetic tapes, a conventional magnetic tape drive is equipped with a head unit having a plurality of data signal recording heads and data signal reproducing heads, respectively. Since in the head unit a data signal recording head or a data signal reproducing head is in charge of recording/reproducing of adjacent data tracks on a magnetic tape, the data signals are recorded/reproduced with moving the data signal recording head or the data signal reproducing head onto a adjacent data track by moving all of the head unit in a lateral direction of the magnetic tape by a minute amount while reciprocating the magnetic tape for the head unit a plurality of times. Therefore, in the conventional magnetic tape drive is introduced a tracking servo technology for controlling a position of the head unit in the lateral direction of the magnetic tape.
The tracking servo technology is a technology where servo signals written on a magnetic tape in advance are read with a servo write head provided at a head unit, a position of the head unit in a lateral direction of the magnetic tape is controlled by driving an actuator in response to the read servo signals, and the data signal recording head or the data signal reproducing head is made to follow a data track. As this kind of a tracking servo technology, for example, in Japanese Patent Laid-Open Publication Hei 8-227511 is disclosed a technology of an amplitude servo system where a plurality of bursts are aligned as servo signals in two lines in longitudinal directions of a magnetic tape. In addition, in Japanese Patent Laid-Open Publication Hei 8-30942 is disclosed a technology of a timing based servo system where timing based signals of a predetermined pattern are recorded as servo signals on a servo track.
In the meantime, the conventional magnetic tape drive forms one piece of data track with one data signal recording head, and then, moves a position of the data signal recording head to a prearranged position where a next data track, which is adjacent to the data track formed now, is formed. Therefore, there are some cases where a predetermined width of margin is provided between adjacent data tracks on a magnetic tape so that a newly formed data track does not overlap a precedingly formed data track due to a control amount error in moving the head unit in the lateral direction of the magnetic tape. And the conventional magnetic tape drive intends to narrow the width of the margin in order to form data tracks in a higher density in the lateral direction of the magnetic tape by heightening an accuracy of a tracking servo.
However, since there exists a limitation in heightening the accuracy of the tracking servo, there is a problem that the conventional magnetic tape drive cannot form the data tracks in the higher density in the lateral direction of the magnetic tape.
Consequently, is strongly requested a magnetic tape drive that can form the data tracks in the higher density in the lateral direction of the magnetic tape, compared to the conventional magnetic tape drive.